The present invention relates generally to fastener-driving tools used to drive fasteners into workpieces, and specifically to combustion-powered fastener-driving tools, also referred to as combustion tools or combustion nailers.
Combustion-powered tools are known in the art. Representative tools are manufactured by Illinois Tool Works, Inc. of Glenview, Ill. for use in driving fasteners into workpieces, and are described in commonly assigned patents to Nikolich U.S. Pat. Re. No. 32,452, and U.S. Pat. Nos. 4,522,162; 4,483,473; 4,483,474; 4,403,722; 5,133,329; 5,197,646; 5,263,439 and 6,145,724 all of which are incorporated by reference herein.
Such tools incorporate a tool housing enclosing a small internal combustion engine or power source. The engine is powered by a canister of pressurized fuel gas, also called a fuel cell. A battery-powered electronic power distribution unit produces a spark combustion within the chamber, while facilitating processes ancillary to the combustion operation of the device. Such ancillary processes include: mixing the fuel and air within the chamber; turbulence to increase the combustion process; scavenging combustion by-products with fresh air; and cooling the engine. The engine includes a reciprocating piston with an elongated, rigid driver blade disposed within a cylinder body.
A valve sleeve is axially reciprocable about the cylinder and, through a linkage, moves to close the combustion chamber when a work contact element at the end of the linkage is pressed against a workpiece. This pressing action also triggers a fuel-metering valve to introduce a specified volume of fuel into the closed combustion chamber.
Upon the pulling of a trigger switch, which causes the spark to ignite a charge of gas in the combustion chamber of the engine, the combined piston and driver blade is forced downward to impact a positioned fastener and drive it into the workpiece. The piston then returns to its original or pre-firing position, through differential gas pressures within the cylinder. Fasteners are fed magazine-style into the nosepiece, where they are held in a properly positioned orientation for receiving the impact of the driver blade. Upon ignition of the combustible fuel/air mixture, the combustion in the chamber causes the acceleration of the piston/driver blade assembly and the penetration of the fastener into the workpiece if the fastener is present.
Such tools are typically employed with nails, brads, or similar fasteners designed for being axially or linearly driven into a workpiece. While these tools have been widely accepted for use in rough framing as well as finish construction, users have been forced to use other tools for installing wallboard to frame members such as metal or wooden studs. In the latter operations, performed on exterior as well as interior construction, users employ corded or cordless drills or fastener drivers for rapidly applying threaded fasteners through the wallboard and into the frame member.
One installation factor dealt with by wallboard installers is that, upon driving, the generally large diameter head of the fastener should be flush with, but not pierce the face paper outer layer of the wallboard. If the fastener passes through the face paper, the board is structurally weakened at that point, and may require additional finishing.
Another installation factor of wallboard installation is that when wallboard is applied to metal frame members, the fastener typically easily passes through the wallboard, but in some cases has difficulty penetrating the frame member. Even when special cutting or drill tip type fasteners are used, the frame member is pushed away from a rear surface of the wallboard. This type of condition has been experienced when combustion tools drive unthreaded fasteners are used to fasten wallboard to frame members, and also when conventional power drills are used to drive wallboard screws. Thus, in some cases, the fastener pierces the frame member on an angle relative to the wallboard. Subsequent tightening of the fastener by the power applicator tool fails to form a tight connection between the wallboard and the frame member at that point.
U.S. Pat. No. 5,862,724 discloses a pneumatic fastener driving tool having both linear and rotational fastener driving functions. One drawback of this tool is that, being pneumatically powered; it requires a remote compressor connected to the tool with a pressure hose. Such hoses are bulky and awkward to work around in many workplaces. Compressors are noisy and cannot always be used indoors. Another drawback of the disclosed tool is that it has insufficient power to drive fasteners into metal frame members. Still another drawback of the disclosed tool is that as the driver blade forces the fastener against the metal frame member, the pneumatic impact force generates recoil which causes a fastener-driving bit at the end of the driver blade to become disengaged from the fastener head. In such cases, a separate tool such as a power screwdriver is needed to complete fastener installation.
Thus, there is a need for a fastener driving tool which addresses the above-identified drawbacks of conventional tools.